grade = input("please input a num in [1-100]:")
#判断输入内容
while True:
    #判断是不是数字
    if bool(grade.isdigit()) == False:
        print("please input a 'num'!")
    else:
        #判断数字是不是在1-100范围内
        if int(grade) < 0 or 100 < int(grade):
            print("please make sure the num in [1-100]")
        else:
            if int(grade) >= 85:
                    print("成绩优秀")
            elif int(grade) >= 60:
                    print("良好")
            else:
                    print("不及格")
    break